1. Field of the Invention
The present invention relates to a battery temperature controller for controlling the temperature of a vehicular battery.
2. Description of the Related Art
Recently, there has been an increasing demand for introducing a low-pollution vehicle and alternative energy vehicle, accompanied with demands for improving the air environment and environmental problems. As a strong candidate for the alternative energy vehicle, there is the hybrid vehicle which uses an electric motor together with an engine. A hybrid vehicle is driven by an engine at the time of high speed driving, and is driven by a drive motor with a battery as a power source at the time of low speed driving. The battery is charged by driving an electric power generation motor at the time of engine driving.
As the battery for the hybrid vehicle, there is for example the lead acid battery, the alkaline storage battery, the metal air storage battery, and the high temperature battery. Of these, the high temperature battery operates stably within a high temperature range (for example 80xcx9c90xc2x0 C.), operating with high efficiency to thereby improve vehicle fuel consumption. That is to say, the high temperature battery of a hybrid vehicle has an optimum efficiency temperature (the influence of temperature on the efficiency is greater than for the conventional lead acid battery) greater than atmospheric temperature, and hence it is desirable to maintain the temperature at around 80xc2x0 C. in consideration of electric generating and storage efficiency and vehicle fuel consumption. As an example of a high temperature battery, there is one which uses a halide of for example copper, nickel, or silver, for the positive electrode, and metallic lithium (alternatively an activated metal such as calcium, magnesium is also possible) for the negative electrode, and employs an organic substance such as propylene carbonate for the electrolyte.
Since it is necessary to mount a heat source for maintaining the temperature of the high temperature battery, on the vehicle, then there is the problem of an increase in vehicle cost and battery cost, and an increase in vehicle size due to the space for mounting the heat source for the battery.
Moreover, since a cooling device is not provided solely for the heat source, then the temperature of the high temperature battery cannot be accurately controlled to an optimum efficiency temperature. Hence there is room for improvement in the efficiency for electricity generation and for electricity storage and in fuel consumption of the vehicle.
The present invention addresses the above problems with the conventional technology with the object of providing a temperature controller for a vehicular battery which uses the waste heat of the engine to heat the high temperature battery, to thereby enable miniaturization of the vehicle and energy savings.
Moreover, another object of the invention is to provide a temperature controller for a vehicular battery which can accurately control the temperature of the high temperature battery to an optimum efficiency temperature.
The temperature controller for a vehicular battery of the present invention, to achieve the above object, comprises a heat exchanger for removing waste heat from a vehicle engine, and a heating loop, being a coolant circulation path, for carrying heat from the heat exchanger to a high temperature battery of a vehicle.
With this invention, the waste heat of the engine is used to maintain the temperature of the high temperature battery, and hence it is not necessary to mount a new heat source in the vehicle. Consequently, miniaturization of the vehicle and energy saving can be achieved.
Furthermore, according to a second aspect of the invention, there is provided; a radiator for cooling the high temperature battery, a cooling loop being a coolant circulation path, for carrying heat from the high temperature battery to the radiator, and connected in parallel with the heating loop so as to have a common path with the heating loop, and a flow control device for the heating loop and the cooling loop.
With this invention, at first at the time of vehicle heating, the heating loop and the cooling loop are respectively in the open condition and the closed condition so that high temperature coolant which has been heated by the engine waste heat in the heat exchanger is circulated in the heating loop to heat the high temperature battery so as to quickly attain the warm-up condition in the high temperature region. After this, in the case where the temperature of the high temperature battery goes above the optimum efficiency temperature, the cooling loop is adjusted so as to open gradually so that low temperature coolant which has given up heat in the radiator is circulated in the cooling loop and mixed with coolant in the heating loop to give a high temperature coolant mixture. Coolant at a fixed temperature is then supplied to the high temperature battery. In this way, the high temperature battery can be operated at an optimum efficiency point.
Here, with a third aspect, for the flow control device, flow control valves may be respectively provided in the heating loop and the cooling loop.
Moreover, instead of respectively providing flow control valves in the heating loop and the cooling loop, a three way valve may be provided at the junction portion of the heating loop and the cooling loop so that the abovementioned temperature control can be effected by operating a single three way valve.